Necrotizing enterocolitis (NEC) is the most common gastrointestinal disease of newborns, and is anticipated to replace pulmonary insufficiency as the leading cause of death in premature babies. We have accumulated multiple lines of evidence supporting a role for heparin-binding EGF-like growth factor (HB-EGF) in protection of the intestines from injury via preservation of the intestinal mucosa. The long term goal of our work is based on the premise that protection of the intestinal mucosa from injury represents a logical target for the development of novel strategies to prevent the disease, and involves the clinical administration of HB- EGF, both therapeutically and prophylactically, to protect neonates from NEC. Recently, we have shown that HB-EGF decreases histologic injury and mortality in a rat model of NEC whereby rat pups are exposed to repeated cycles of hypoxia/hypothermia, hypertonic feedings and exposure to LPS (HHHTF+LPS), leading to intestinal lesions indistinguishable from those of human NEC. Our central hypothesis is that tissues afflicted with NEC have a local deficiency of HB-EGF which leaves a portion of the intestine susceptible to injury, and that administration of exogenous HB-EGF protects the intestine from injury via promotion of intestinal restitution, thereby preserving intestinal permeability. Towards our goal, we have proposed three specific aims that will allow a better understanding of the mechanistic basis of HB-EGF function in injured intestine, as a prerequisite to developing therapeutic clinical protocols: Aim [1] To test the hypothesis that HB-EGF gain-of-function will lead to resistance to NEC whereas HB-EGF loss-of-function will lead to increased susceptibility to NEC. We will subject neonatal HB-EGF transgenic and knockout mice to experimental NEC by exposing them to HHHTF, with evaluation of gut barrier function by systemic absorption of enteral FICT- dextran, Ussing chamber ex vivo studies and determination of bacterial translocation;intestinal histology;and mortality. Aim [2] To test the hypothesis that HB-EGF protects the intestine in vivo by inducing mediators of intestinal restitution during HHHTF-induced NEC. The mouse model of NEC will be used in HB- EGF TG, HB-EGF KO and WT mice, with measured endpoints including mRNA expression and protein production of mediators of restitution (integrins, FAK, paxillin, Rho). Ex vivo Ussing chamber studies will also be performed to further examine the mechanisms by which HB-EGF promotes intestinal restitution. Aim [3] To test the hypothesis that HB-EGF promotes restitution by affecting epithelial cell-matrix interactions. The in vitro scrape-wounding model of restitution will be utilized to examine the molecular mechanisms utilized by HB-EGF to promote restitution. The relevance of this research to public health is that it will provide a better understanding of the mechanisms utilized by HB-EGF in protection of the intestines from NEC, as a prerequisite for the development of HB-EGF-based therapeutic regimens.